Four new tetragonal superhard sp3 carbon allotropes with wide direct band gaps

Abstract

In this study, four new tetragonal sp3 carbon allotropes with high dynamic and mechanical stabilities (I41/acd-C112, I4/mcm-C128, I4/mcm-C112, and I41/amd-C64) were predicted using first-principles calculations. The I41/acd-C112, I4/mcm-C128, I4/mcm-C112, and I41/amd-C64 allotropes exhibited semiconductor behavior, as confirmed by their wide band gaps (calculated to be 3.80, 3.22, 3.56, and 3.51 eV, respectively) and superhardness, as evidenced through hardness and ideal strength calculations.

Keywords

• Carbon allotropes
• First-principles calculations
• Superhard materials